2,7,15,17-Octadecatetraenal,5,11-bis[[(1,1-dimethylethyl)dimethylsilyl]oxy]-13-hydroxy-4,6,8,10,12,14-hexamethyl-, (2Z,4S,5S,6S,7Z,10S,11R,12R,13S,14S,15Z)-